The present invention is generally directed to ink compositions, and more specifically the present invention is directed to specific compositions useful in ink jet printing systems, and to processes for the preparations thereof. Accordingly, in one embodiment of the present invention there are provided aqueous ink compositions comprised of certain dyes with solubility in the solvent selected, and substantial insolubility in water. Therefore, in one preferred embodiment of the present invention the ink compositions are comprised of water, specific organic solvents inclusive of Sulfolane.RTM., and spirit solvent dyes with solubility in the aforementioned solvents and substantial insolubility in water. The ink compositions of the present invention in addition to possessing the improved characteristics indicated hereinafter, such as excellent waterfasteness, are useful in various imaging and printing processes inclusive of thermal ink jet or bubble jet wherein the ink is heated to its boiling temperature enabling the injection of a bubble, reference U.S. Pats. Nos. 4,243,994; 4,325,735; and 4,396,429, the disclosures of which are totally incorporated herein by reference; as well as British Patent Publications Nos. 2,007,162 and 2,060,499, the disclosures of which are totally incorporated herein by reference.
Compositions which are useful in ink jet printing systems are well known, and generally contain water soluble dyes. There is thus disclosed, for example in U.S. Pat. No. 3,846,141, an ink composition useful in jet printing comprised of an aqueous solution of a water-soluble dye; and a humectant material formed of a mixture of a lower alkoxy triglycol and at least one other compound selected from the group consisting of a polyethylene glycol, a lower alkyl ether of diethylene glycol, and glycerol. The humectant system disclosed in this patent substantially prevents or minimizes tip drying of the printing ink in the orifice or nozzle during down time of the printer, such as when the printer is rendered inoperative. As further disclosed in this patent, the basic imaging technique in jet printing involves the use of one or more ink jet assemblies connected to a pressurized source of ink. Each individual ink jet includes a very small orifice usually of a diameter of 0.0024 inches, which is energized by magneto restrictive piezo-electric means for the purpose of emitting a continuous stream of uniform droplets of ink at a rate of 33 to 75 kilohertz. This stream of droplets is desirably directed onto the surface of a moving web of, for example, paper; and is controlled to form printed characters in response to video signals derived from an electronic character generator and in response to an electrostatic defletion system.
Furthermore, there are illustrated in U.S. Pat. No. 4,295,889 recording liquid ink compositions, and more specifically liquid compositions for use in a recording system wherein the liquid recording component is jetted from a small orifice in a form of a droplet. According to the disclosure of this patent the recording liquid composition comprises a compound of the general formula (A) as illustrated in column 3, beginning at line 30, or compound of the general formula (B), reference column 3, beginning at line 47, which components are referred to as dye compounds, see column 4, line 28. Example of numerous dyes are provided beginning at column 4, line 51, and continuing on to column 42 for example. In column 43, beginning at line 29, of the U.S. Pat. No. 4,295,889 there are disclosed examples of water soluble organic solvents useful as a carrier component together with water, which solvents include alkylene glycols containing 2 to 6 carbon atoms in the alkylene moiety; and moreover, it is stated in column 44, beginning at line 8, that the properties of the liqquid developer may be further improved by adding additives including nitrogen containing compounds such as 1,3-dimethyl-2-imidazolidinone, see column 44, line 22. Other patents containing similar teachings include U.S. Pat. Nos. 4,325,735; 4,395,287; 4,395,288; and 4,396,429. There is no disclosure in these references however, with respect to ink compositions containing spirit soluble dyes with, for example, higher solubility in certain nonvolative organic solvent phase than in water thereby avoiding ink clogging caused primarily because of water evaporation. Thus, with the inks of the present invention, ink jet clogging is avoided and other advantages are achievable especially because, for example, of the intrinsic low water solubility or insolubility of the spirit soluble dyes which enables, for example, improved waterfastness characteristics as compared to inks wherein typical water soluble acid dyes and direct dyes are selected. Furthermore, the ink composition of the present invention with the spirit soluble dyes permit the presence of greater quantities of the organic phase solvent in the aforementioned inks, for example up to 80 percent, thereby rendering these inks susbstantially more compatible with typical transparency materials.
Also, there is disclosed in U.S. Pat. No. 4,279,653 ink jet compositions containing water-soluble wetting agents, a water-soluble dye and an oxygen absorber. Similarly, U.S. Pat. No. 4,196,007 describes an ink jet printing composition containing an aqueous solution of a watersoluble dye and a humectant consisting of at least one water-soluble unsaturated compound. Further, there is disclosed in U.S. Pat. No. 4,267,088 coatings particularly useful as marking inks wherein there is selected an epichlorohydron - modified polyethylenimine, and an ehtylene oxide modified polyethylenimine in an aqueous solution. Other patents of intereat are U.S. Pat. Nos. 4,101,329; 4,290,072; 4,383,859; 4,235,773; 4,279,814; 4,443,371; 4,286,989; 4,299,630; 4,167,393; 3,864,296; 4,238,234; 3,234,025; 4,520,143; 3,920,855; and 4,182,612.
Additionally, there is disclosed in U.S. Pat. No. 4,197,135 ink compositions with improved waterfastness comprised of at least one water soluble dye, and a polyamine with 7 or more nitrogen atoms per molecule. Specifically, there is illustrated in this patent an ink composition comprising an aqueous solution of at least one water-soluble dye, and about 0.5 percent to about 10 percent by weight concentration of a polyamine having 7 or more nitrogen atoms per molecule; and wherein the composition has a pH of 8 or above. In column 1, beginning at line 61, of this patent it is indicated that the preferred polyamines have the hydrogen of the primary amine group replaced with either a methyl or a hydroxyethyl group. Examples of fully substituted polyamines selected are outlined in column 2, beginning at line 40, of the U.S. Pat. No. 135.
Further, there is disclosed in U.S. Pat. No. 4,659,382 entitled "Waterfast Ink Jet Compositions and Process", the disclosure of which is totally incorporated herein by reference, ink compositions comprised of hydroxylated polyethylenimines, dyes and water. More specifically, there are described in this patent inks with a major amount of water, a hydroxyethylated polyethylenimine polymer, and a dye component wherein the polymer has incorporated therein from about 65 percent by weight to about 80 percent by weight of hydroxyethyl groups. Additionally, illustrated in U.S. Pat. No, 4,664,708 entitled "Waterfast Ink Compositions", the disclosure of which is totally incorporated herein by reference, are ink compositions comprised of water and a polymeric dye comprised of water soluble polymers with highly stable chromophores covalently bonded thereto. Specifically, there are described in this patent inks with a major amount of water, and a polymeric dye comprised of the reaction product of a water soluble polymer with a reactive dye.
Although many of the above compositions are suitable for their intended purposes, there continues to be a need for other ink compositions and processes thereof. Specifically, there is a need for ink jet compositions with excellent waterfastness characteristics, and wherein, for example, the dyes selected are retained in solution rather than forming as precipitates, and thereby causing clogging of the ink jet nozzles. Additionally, there is a need for ink compositions with excellent color intensities, and wherein, for example, the amount of dyes selected can be deacresed for example only about 1 percent of dye is needed with the inks of the present invention in some situations as compared to about 3 to 5 percent with the direct dyes of the prior art. Furthermore, there is a need for ink compositions wherein the waterfastness is greater than about 80 percent. Also, the inks of the present invention possess other desirable characteristics including acceptable viscosity parameters, suitable surface tension values, excellent color intensity especially with respect to the black inks; and these inks enable the retention of the dye molecules therein thereby preventing percipitation and undesirable clogging of the ink jet nozzles. Other important characteristics associated with the inks of the present invention include the enablement of permanent transparency formation, and the continued solubility of the inks including solubility subsequent to evaporation of the water contained therein.